package chapter2;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;


/**
 * Basic symmetric encryption example with padding
 */
public class SimpleSymmetricPaddingExample {
    public static void main(
            String[] args)
            throws Exception {
        byte[] input = new byte[]{
                0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
                0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
                0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17};
        byte[] keyBytes = new byte[]{
                0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
                0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
                0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17};

        SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");

        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "BC");


        System.out.println("input : " + Utils.toHex(input));

        // encryption pass

        cipher.init(Cipher.ENCRYPT_MODE, key);

        byte[] cipherText = new byte[cipher.getOutputSize(input.length)];

        int ctLength = cipher.update(input, 0, input.length, cipherText, 0);

        ctLength += cipher.doFinal(cipherText, ctLength);

        System.out.println("cipher: " + Utils.toHex(cipherText) + " bytes: " + ctLength);

        // decryption pass

        cipher.init(Cipher.DECRYPT_MODE, key);

        byte[] plainText = new byte[cipher.getOutputSize(ctLength)];

        int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);

        ptLength += cipher.doFinal(plainText, ptLength);

        System.out.println("plain : " + Utils.toHex(plainText) + " bytes: " + ptLength);
    }
}
